1. Field of the Invention
The present invention relates to a cleaning device for a light transmission member, and to an electrophotographic image forming apparatus such as a laser printer, a facsimile apparatus, or a copying machine equipped with the same.
2. Description of the Related Art
Conventionally, an apparatus equipped with a light transmission member has been equipped with a cleaning device for removing a stain on the transmission member. For example, in an electrophotographic image forming apparatus, there is provided, at a light irradiation opening of a light irradiation unit for irradiating a photosensitive member with light, a light transmission member such as a cover glass, in order that foreign matter such as toner and dust scattered within the apparatus may not enter the light irradiation unit, with there being provided a cleaning mechanism for cleaning the transmission member.
Japanese Patent Application Laid-Open No. 2008-242432 discusses a configuration in which, in order that a reduction in image density or partial image omission may not be caused by foreign matter adhering to the transmission member, a cleaning member having contact with the transmission member is configured to make a reciprocating movement by inserting and extracting a cartridge into and out of the apparatus main body, thereby removing foreign matter adhering to the transmission member. Further, according to Japanese Patent Application Laid-Open No. 2008-242432, this configuration also prevents the foreign matter which adheres to the cleaning member at the time of cleaning of the transmission member from adhering to the transmission member again, thereby protecting the transmission member from being soiled. More specifically, on the forward way (at the time of insertion of the cartridge), the cleaning member is held in contact with the transmission member to clean the transmission member, and, on the backward way (at the time of extraction of the cartridge), the cleaning member is spaced away from the transmission member so that the cleaning member is restored to a cleaning start position without cleaning the transmission member.
However, in the configuration of Japanese Patent Application Laid-Open No. 2008-242432, in which, in order that the foreign matter adhering to the cleaning member may not be allowed to adhere to the transmission member again, the cleaning member is configured to clean the transmission member solely on the forward way (at the time of insertion of the cartridge), and is not configured to clean it on the backward way (at the time of extraction of the cartridge). The frequency of cleaning is therefore rather low with respect to the number of times that the cleaning member is moved, so that there is a fear of the transmission member not being sufficiently cleaned.
In recent years, in particular, in order to suppress the increase in the interior temperature of the apparatus due to the recent increase in the operating speed of image forming apparatuses, there is a tendency for the amount of cooling air blown within the apparatus to increase, with the result that foreign matter such as toner and dust within the apparatus is likely to be scattered, making the transmission member more subject to staining. Further, depending upon the arrangement of the light irradiation unit inside the apparatus, the configuration of the cartridge, and the direction of the airflow inside the apparatus, there are cases where the transmission member is subject to staining even when the amount of air blown is not large.
The above problem might be solved by increasing the frequency at which cleaning is performed by the cleaning member. One possible method of doing so might be to bring the cleaning member into contact with the transmission member in both the forward and backward ways. However, as described above, simply bringing the cleaning member into contact with the transmission member in both the forward and backward ways would result in the foreign matter which adheres to the cleaning member on the forward way being allowed to adhere to the transmission member again on the backward way, thus staining the transmission member.
Another possible method of increasing the cleaning frequency might be to increase the number of times that the cleaning member is moved. However, in a configuration in which the movement of the cleaning member is performed in relation to the movement of another component (e.g., the cartridge), the movement frequency of the cleaning member depends on the movement frequency of that component, which means it is rather difficult to enhance solely the movement frequency of the cleaning member alone. Even if there is to be provided a dedicated operation for moving the cleaning member, there will be involved a problem due to an increase in the frequency of the operation. For example, there will be involved an increase in the time period in which image formation cannot be executed due to the movement of the cleaning member. In the case where it is a user or a serviceman that executes the operation, the burden on the user or the serviceman would increase.